Polyarylates are aromatic polyesters derived from dihydric phenols and aromatic dicarboxylic acids. The material based on 2,2-bis(4-hydroxyphenyl)propane (bisphenol-A) and a 50:50 mixture of terephthalic and isophthalic acids (1) is offered commercially by Amoco Performance Products, Inc. under the tradename of ARDEL D-100.RTM.. ##STR1## Polyarylates are high temperature, high performance thermoplastic polymers with a good combination of thermal and mechanical properties. They display excellent UV resistance and have good processability which allows them to be molded into a variety of articles.
A drawback of polyarylates is their lack of good solvent, chemical and environmental stress-crack resistance.
Aliphatic and aliphatic-aromatic polyamides, depending on their composition, are either crystalline or amorphous. The crystalline versions display high melting points and provide a class of polymers with good high temperature properties. The amorphous aliphatic-aromatic polyamides show high glass transition temperatures. Both have good mechanical properties, solvent, chemical and stress-crack resistance. Polyamides have been described-see, for example, J. Zimmerman, Encyclopedia of Polymer Science and Engineering, 2nd. Edition, Vol. 11, pp. 315-381, John Wiley and Sons, Inc., New York, N.Y., 1988.
It has now been unexpectedly discovered that a block polymer of polyarylates-polyamides can be produced and that it has superior U.V. resistance, good processability and good solvent, chemical, and stress crack resistance. Furthermore, a new method to prepare these copolymers, having a well-defined structure, has been developed. It is found that polyarylates having at least one terminal dihydroarylcyclobutene group per chain, react with polyamides having at least one terminal ethylenically unsaturated double bond per molecule, to give the present polyarylate-polyamide block copolymers.
Block copolymers containing polyamide and polyester segments have been described. U.S. Pat. No. 4,258,154 discloses a resin composition consisting essentially of (A) an aromatic polyester-polycarboxylic anhydride and (B) a polyamide. The reference implies that a reaction of the terminal amino group of the polyamide with the anhydride group of the polyester takes place upon blending; a chemical bond between the two polymers is created. Allegedly, a blend with improved mechanical properties is obtained. U.S. Pat. No. 4,417,031 discloses a process for preparing block and/or graft copolymeric compositions by forming an intimate mixture of two or more polymers, at least one of which includes one or more amino junctions, and at least one of the remaining polymers includes one or more carboxylic acid junctions and an effective amount of a phosphite compound. The mixture is then heated at a temperature and for a time sufficient to form the desired block, and/or graft copolymers. Clearly, both of the cited patents yield ill-defined mixtures.
Polymers based on dihydroarylcyclobutenes are known in the literature. U.S. Pat. No. 4,540,763 describes the formation of thermosets by thermally reacting poly(dihydroarylcyclobutenes). Thermosetting materials may be formed via a similar reaction from bifunctional dihydrobenzocyclobutene-alkyne imide monomers, as described in U.S. Pat. No. 4,675,370 and in the Journal of Polymer Sci., Polymer Chemistry 25, p. 3159 (1987); a related reaction, the formation of thermosetting polymers by heat-treating alkynyl-bridged poly(dihydroarylcyclobutenes), is disclosed in U.S. Pat. No. 4,687,823. The formation of crosslinked products is also the subject of U.S. Pat. Nos. 4,687,815 and 4,708,994 and of European Patent Application No. 227,124. Dihydrobenzocyclobutene end-capped styrene, diene, or styrene-diene copolymers were shown to be capable of thermally induced coupling-see U.S. Pat. No. 4,708,990. Difunctional dihydroarylcyclobutenes, such as the 4,4'-ethylidene dibenzocyclobutene, were used as crosslinking agents for ethylene-propylene-diene rubbers, as described in European Patent Application No. 227,163. Adhesives capable of bonding steel substrates have formed via the thermal polymerization in situ of arylcyclobutenes, such as N-7(benzocyclobutene-4-carboxamido)heptylbenzocyclobutene-4-carboxamide, and are disclosed in PCT Int. Appl. No. WO 87/01,383. U.S. Pat. No. 4,719,283 claims thermoplastic polyimides made by the reaction of bis-maleimides with substituted derivatives of (2) below. ##STR2##